WL#7199: True bottom-up server parser: common framework for the refactoring

This is a design WL for the common bottom-up parser refactoring framework.
This worklog implements one step in the overall task to "Refactor MySQL server
parser to build the AST in a natural "bottom-up" way".
One of design goals is to have larger syntax rules in the future, leading to
fewer (but larger) intermediate nodes in the parse tree. The argument is that
this will give fewer node allocations and hopefully also a faster grammar, as
there are fewer rules all together.